1. Technical Field
This invention relates to a device for switching between normal and reverse drive force, a feeder for switching between normal and reverse directions using this device, and a driving device for paper feed rollers of e.g. office machines using this feeder.
2. Background Art
Since paper is ordinarily fed in a paper feeder of an office machine in one direction, its drive mechanism is driven by a motor that rotates in one direction only. In a more advanced paper feeder that can switch over the paper feed direction, a device for switching the motor drive rotation between normal and reverse had to be added if a conventional unidirectional motor is used for the machine (Patent Document 1).
As a mechanism for switching between normal and reverse drive force in such a case, a mechanism using three bevel gears shown in FIG. 54 is known (Non-Patent Document 1). In this mechanism, an output shaft 103 is provided near the flank of an input bevel gear 102 and perpendicularly to an input shaft 101, and a clutch 104 is axially slidably keyed to the output shaft 103. On both sides of the clutch 104, a pair of bevel gears 105 are rotatably fitted and meshed with the input bevel gear 102. Teeth 107 engaging the clutch 104 are formed on boss portions 106 provided on the opposed sides of the respective output bevel gears 105. In a circumferential groove 108 formed in the center of the clutch, a pin 110 for a rocking arm 109 is inserted. The other end of the rocking arm 109 is pivotally mounted on a on a fixed portion by means of a shaft 111.
When the rocking arm 109 is inclined to left or right, the clutch 104 slides in the axial direction and is engaged with the teeth 107 of the output bevel gear 105 on the side toward which the rocking arm 109 is inclined. Thus, the rotation of the input shaft 101 is transmitted to the output shaft 103. When the rocking arm 109 is inclined toward the other side, the clutch 104 is engaged with the output bevel gear 105 on the opposite side and the output shaft 103 rotates in the opposite direction.    Patent Document 1: Japanese Patent Publication 05-307290 A    Non-Patent Document 1: Page 81 of “Kinematic Mechanism of Machinery” published by Gihodo Shuppan Co., Ltd. on Oct. 15, 1957
In the above-mentioned device for switching over the drive force, since the input shaft 101 and the output shaft 103 extend perpendicular to each other, the layout of a motor on the input side and feed rollers on the output side was limited. Also, the diameter of the input bevel gear 102 became larger and the control mechanism of the rocking arm 109 became complicated. Further, means for synchronizing the rotation phase of the teeth 107 was required when switching the clutch to avoid collision of the teeth.